The radial distribution of lubricating fluids from a rotating shaft is basically well known to the prior art. Typically, a rotating shaft may have a feed passage which extends axially within the rotating shaft. One or more radially oriented discharge ports communicate between the axially oriented feed passage and the exterior of the shaft. Rotation of the shaft ejects lubricating fluid, from that present within the axially oriented feed passage, radially outwardly through the discharge ports to at least some extent by centrifugal action. Such distribution systems for lubricating fluid have been widely employed in the automotive industry to effect lubrication of bearings, gears and other relatively moving elements. Radial distribution of lubricating fluid has, perhaps, been most frequently adopted for use in conjunction with vehicular transmissions.
U.S. Pat. No. 4,442,729 to Hayakawa, issued Apr. 17, 1984, discloses a structure which exemplifies the radial distribution of lubricating fluid from a rotating shaft according to the prior art. As is customary with such prior art distributing systems, this patent discloses the use of an axial feed passage within a rotating shaft. A plurality of radially oriented discharge ports effect communication between the feed passage and the exterior of the rotating shaft. This prior art patent discloses a pressurized feed system. That is, lubricating fluid is pumped, under pressure, into the feed passage, and as the shaft rotates the lubricating fluid is distributed outwardly through the radially oriented discharge ports to lubricate various elements of a four-wheel drive, torque transfer mechanism.
U.S. Pat. No. 4,644,815 to Nagoyo et al., issued Feb. 24, 1987, on the other hand, discloses the use of a gravity system to supply lubricating fluid to the feed passage. The gravity supply system includes an oil collecting assembly mounted above the rotating shaft which has the axial feed passage therein. The lubricating fluid splashes against the collecting assembly and is directed to the entrance of the feed passage within the shaft. Specifically, a conduit directs the lubricating fluid from the collecting assembly to an impeller in the open end of the feed passage. The impeller causes the lubricating fluid to flow toward the closed, or downstream, end of the feed passage. Rotation of the shaft effects radial distribution of the lubricating fluid outwardly through a plurality of axially spaced, radially disposed, discharge ports.
U.S. Pat. No. 4,222,283 to Nagy, issued Sept. 16, 1980, also discloses a gravity system for supplying lubricating fluid to the axial feed passage within the rotating shaft of a radial distribution system for lubricating fluids. Here, too, the lubricating fluid is splashed against a collecting assembly positioned above the rotating shaft within which the feed passage extends. The collection system disclosed in this prior art patent works exceptionally well, and such a system can well be employed in conjunction with the present invention. In any event, the lubricating fluid so collected is then fed, via gravity, past a sleeve and retaining shield mounted adjacent to the open, or upstream, entry end of the feed passage within the rotating shaft in order for the lubricating fluid to gain admission to the feed passage. The sleeve and retaining shield permit lubricating fluid to flow into the feed passage during rotation of the shaft, but the sleeve and retaining shield also attempt to retain a portion of the lubricating fluid within the feed passage at shutdown in order to provide some lubricating fluid for radial delivery immediately upon start-up. The effectiveness of this attempt will, of course, depend at least in part on the disposition of the discharge ports when the shaft stops rotating.
It has been found that systems for radially distributing lubricating fluid by rotation of a shaft work quite well when there are a limited number of axially spaced discharge ports. In this regard it should be understood that rotation of the shaft acts upon the lubricating fluid as soon as it enters the feed passage. For that reason the major portion of the lubricating fluid is emitted from the discharge ports located in closest proximity to the locus at which the lubricating fluid is admitted to the feed passage. Accordingly, when a plurality of discharge ports are spaced axially along the feed passage--and particularly when a gravity feed system is employed--comparable quantities of lubricating fluid are not necessarily emitted from each discharge port. The greatest quantity of lubricating fluid is generally emitted from that discharge port located in closest proximity to the locus at which the lubricating fluid is admitted, with progressively lesser quantities being emitted from the successively more remote discharge ports. Some attempts have been made to vary the size of the individual discharge ports in order to achieve the emission of comparable quantities of lubricating fluid from the successively more remote discharge ports, but such an approach is effective only with respect to any shaft which is rotated at a fairly constant speed. The prior art is, therefore, devoid of structures which are capable of assuring the delivery of comparable quantities of lubricating fluid through a plurality of axially spaced, discharge ports, and particularly so when the shaft is subjected to rotation at varying speeds as well as when a gravity system is employed to deliver lubricating fluid to the feed passage.